Surface acoustic wave sensors can be utilized in a variety of sensing applications, such as torque, pressure and/or temperature detection. Such sensors can be implemented, for example, by locating surface acoustic wave (SAW) device on an etched diaphragm within a piezoelectric material such as quartz. To date, however, technological hurdles have prevented such devices from being effectively implemented. Currently, a strong demand exists to utilize torque, pressure and/or temperature sensors in harsh environments or in association with rotating parts.
Attempts have been made to implement pressure sensing devices. A number of problems, however, are associated with conventional sensor applications. For example, in a SAW sensor, mechanical strain affects both the propagation path length and wave velocity. Changes in frequency and/or phase thus correlate with this strain. In conventional, SAW torque sensor designs, for example, one or two SAW chips have been implemented in a torque sensor configuration. The use of such devices, however, results in increased production costs, larger chip sizes and is difficult to micro-machine. Existing designs therefore require large substrate and circuit sizes, and also expensive calibration processes during production.
A need therefore exists for improved SAW sensor applications, particularly those involving torque, pressure and/or temperature sensing. It is believed that a micromachined approach, as disclosed herein, can overcome the aforementioned problems inherent with conventional sensing systems.